Transcript Genetics Slides - The Adapa Project

Sequencing Our Genome:
Background
Bio 101
How can a black female dog have yellow,
brown, and black puppies?
A Simple Cross: Mendel’s Peas
Mendel’s explanation for the flow of
genes in matings
Mendel’s experimental test
Two genes…
What would a test cross for two genes
look like?
What would a test cross for two genes
look like?
YyRr x yyrr
| YR
Yr
yR
yr
------|-------------------------------------yr | YyRy Yyrr yyRr yyrr
yr | YyRy Yyrr yyRr yyrr
yr | YyRy Yyrr yyRr yyrr
yr | YyRy Yyrr yyRr yyrr

4
1
:
:
4
1
:
:
4
1
: 4,
: 1
OR
Two genes are needed for a black female
dog to have three colors of puppies
Pedigrees trace genes in families
A vertical pattern of inheritance indicates
a rare dominant trait.
Huntington’s disease: A rare dominant trait (“vertical pattern”)
Assign the genotypes by working backward through the pedigree
1. All affected individuals have an affected parent.
2. About ½ of all children from an affected parent are affected.
A horizontal pattern of inheritance
indicates a rare recessive trait.
Cystic fibrosis: a recessive condition (“horizontal pattern”)
1. Unaffected parents can produce affected children.
2. About ¼ of children are affected in families with the trait.
3. “Consanguinous” marriages may be involved.
4. Heterozygotes are called “carriers.”
5. All
of the©children
of affected
individuals must carry
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The McGraw-Hill
Companies,
2-12(or express) the trait.
Fig.2.22Inc. Permission required to reproduce or
CQ#1: What is this pedigree telling us?
personal genetics education project
Deciphering a Pedigree
Example: A family where a trait appears in 2 out of 3 children
Dad
Son
(unaffected)
Mom
Twin son
(affected)
Twin daughter
(affected)
personal genetics education project
Short applications
 A family has one child with cystic fibrosis. What is the
probability that the next child will also have it? Be a carrier?
 If a man with sickle-cell disease (recessive) marries a normal
woman, what is the probability that their first child will have
the disease?
 BRCA1 mutations are associated with increased cancer rates
on both men and women. What is the probability that the
first child of a woman with a BRCA1 mutation (dominant)
will have an increased probability of cancer?
CQ#2 – What Can We Learn From This Pedigree?
Maria
Steven
age 60
breast cancer
Vanessa
Emily
Angela
Malcolm
XX
Chris
Ashley
personal genetics education project
What if we cannot SEE differences
in DNA?
 Coat color, pea color, Huntington’s disease, sickle cell
anemia, and cystic fibrosis can be tracked in famiies because
the genes create visible changes.
 BRCA-1 and most other genes either:
 Do not create a visible genotype, or
 The genotype appears too late to be useful for diagnosis or
treatment.
 HOW CAN WE TRACE IMPORTANT GENES IF WE
CANNOT SEE THEM?
CQ#2 – What We Learn From Genetic Screening
Maria
Steven
age 60
breast cancer
Vanessa
Emily
Angela
Malcolm
XX
Chris
Ashley
Ages 22-37
personal genetics education project